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Why Is Blood Sugar Highest in the Morning?


Many people with diabetes find that their fasting blood sugar first thing in the morning is the hardest blood sugar to control. In addition, they find that if they eat the same food for breakfast as they do for lunch or dinner they will see a much higher blood sugar number when testing after breakfast than they see at the other meals.


The reason for this is a normal alteration in hormones experienced by many people not just people with diabetes. It is called "Dawn Phenomenon."


What Causes Dawn Phenomenon?


The body prepares for waking up by secreting several different hormones.


First, between 4:00 and 6:30 a.m. it secretes cortisol, epinephrine, and norepinephrine. You may recognize these as the hormones involved in the "fight or flight response." In this case, their job is more benign, to give you the energy to get up and moving so you can find the food your body needs for energy.


To help you do this, these hormones also raise your blood sugar. After a long night's sleep, the fuel your body turns to to get you going is the glucose stored in the liver. So after these stress hormones are secreted, around 5:30 a.m., plasma glucose rises. In a person with normal blood sugar, insulin will also start to rise at this time but many people with diabetes won't experience the corresponding rise in insulin. So instead of giving their cells a dose of morning energy, all they get is a rise in blood sugar.


Not Everyone Experiences Dawn Phenomenon


Researchers who have infused different hormones into experimental subjects have found that the trigger for dawn phenomenon is a nocturnal surge in growth hormone. If they block the growth hormone, blood sugars stay flat.


This may explain why some people, particularly older people, do not experience a rise in blood sugar first thing in the morning. They may no longer produce significant amounts of growth hormone.


It's possible that people who are "morning people," the ones who bound out of bed filled with energy have a stronger growth hormone response, too. Those of us, no matter what our blood sugar status, who drag out of bed half dead and need three hours to get going and are at our best later in the day, may not.


Another reason that may explain why some people with diabetes do not see a surge in their early morning fasting blood sugar may be that this rise is relatively slow and may be countered by what is left of their basal insulin production.


In people whose diabetes is caused primarily by a flaw in first phase insulin response--the response to the sudden sharp rise in glucose caused by a meal--the basal response may still be strong enough to keep the blood sugars controlled.


We Are All More Sensitive to Carbs in the Morning


Even people with normal or near normal blood sugars experience much higher blood sugars after eating a high carbohydrate breakfast. This was demonstrated in the CGMS study discussed in the post What is a Normal Blood Sugar.


The reasons for this are not yet known, but may turn out to be a result of early morning changes in the liver caused by the dawn phenomenon hormones.


Whatever the reason, you can expect to see higher blood sugars if you eat carbohydrates for breakfast than you will if you eat them later in the day, even if you are on medications.


The Somogyi Effect A.K.A. The Counterregulatory Response


If you read about dawn phenomenon online you will often see the "Somogyi Effect" cited as a cause. This term refers to a phenomenon also known as a "counterregulatory response." It occurs when the blood sugar drops low enough to alarm the body into thinking a dangerous hypo is occurring. When this happens, the body releases stress hormones and glucagon (the hormone secreted by alpha cells in the pancreas that works to raise blood sugar). These cause the liver to dump some of the glucose it has stored in the form of glycogen to raise the blood sugar back to the safety zone. After this happens, the body becomes more insulin resistant for several hours afterwards.


The usual cause for this kind of low is taking too much basal insulin at night, especially if you are a Type 2 who still produces a tiny bit of your own. If you are going to go low it will usually happen between 3 AM and 4 AM.


A counter-regulatory response and the burst of stress hormones it releases not only raise the blood sugar, it may also cause you to wake up suddenly after a nightmare or with your heart pounding. But by the time you experience the impact of the stress hormones your blood sugar will have risen in response to them and you won't see a low on your blood sugar meter. To see if a low is causing the blood sugar rebound you would have to have tested earlier, before the time you were woken up by the response.


Sometimes when you test after a burst of stress hormones caused by an early morning low you will actually see an elevated fasting blood sugar. If you aren't aware that a low caused this morning surge and increase your basal insulin dose you can actually make things worse. So if increasing your basal insulin dose ever makes your blood sugar rise, suspect that you are getting a low sometime in the very early morning hours.


Dr. Richard K. Bernstein casts doubt on whether the Somogyi Effect is real, blaming a strong blood sugar rebound after a low on the high doses of carbohydrates many people on insulin use to correct lows. However, I have experienced this rebound effect myself when I was taking too much basal insulin or, for that matter, too much R insulin at dinner, so I have no doubt it occurs.


I noticed that a raising my dose of dinner insulin too high always resulted in a higher, rather than lower blood sugar the next morning. The rise would be about 20 mg/dl (1.1 mmol/L). Eating 10 grams of carbs before bed eliminated the problem, and I would see a lower blood sugar the net morning. So did lowering the dinner dose of insulin.


Another Unsuspected Cause of Morning Rebound Blood Sugars--Too Much Blood Pressure Medication

Taking a bit too much blood pressure medication can also cause your blood sugar to go up first thing in the morning. That is because if your blood pressure drops too low at night, your body will secrete those same stress hormones to raise it back into the safe zone. These stress hormone have the side effect, as we've seen, of raising blood sugar.


Again, the tip-off that this is happening is that you are likely to wake up at 3 or 4 a.m. with your pulse pounding, sometimes you will think this is because of a vivid nightmare, but it is more likely that the nightmare was a response to the surge of stress hormones that raised your blood pressure.


If you measure your blood pressure after waking, the main thing you'll see is a faster pulse. The blood pressure will be back in the normal or even slightly high zone. If you raise your dose of blood pressure medication because the blood pressure is too high first thing in the morning, you may make the situation worse!


If you are waking up with a pounding pulse in the early morning hours and see your morning blood sugar rising, too, talk to your doctor about whether your blood pressure medication needs adjustment.


I have had a doctor pooh-pooh this explanation, but I have found that lowering the dose of my blood pressure medication after experiencing early morning waking always improves my blood pressure.


Too much blood pressure medication can become an issue for people who have cut back on their carbohydrates. That is because very often, as you bring down your blood sugar by cutting down on your carbohydrates, your blood pressure will start dropping, too, even if you haven't lost significant amounts of weight. At that point an adjustment will be needed. Metformin also can lower blood pressure naturally after you have taken it for several months.

How Do You Lower High Fasting Blood Sugars?


Take the Load Off Your Beta Cells at Meal Time

For many of us the answer is by bringing down our post-meal blood sugars. If your beta cells aren't spending four or five hours trying to bring down a very high post meal blood sugar, they may be able to secrete enough basal insulin to bring down the fasting blood sugars.


That was certainly my experience. I was unable to lower my fasting blood sugars through diet alone even when cutting carbohydrates down to less than 12 g per meal. However, when I started using using mealtime insulin to control my post-meal blood sugars I saw a 25 mg/dl (1.4 mmol/L) drop in fasting blood sugar over several months.

Try a Before-Bed Snack

Some people find that they can reduce their fasting blood sugar by eating a small snack before bed. Some people use a protein snack, which can be thought of as "slow release carbohydrate" since about 60% of protein turns into carbohydrate over a seven hour period. Others find a couple crackers or a pretzel helps.

Split Basal Insulin into Two Doses

Another solution if you are on a basal insulin and believe you are going low in the early morning hours may be to split your daily dose into two and take a larger dose in the morning and a smaller dose 12 hours later. Talk to your doctor about adjusting your dose if you believe you are going low.


Another alternative is to try the new insulin, Tresiba, if your insurance will cover it. Some people are reporting much smoother blood sugars when taking this new basal insulin.


Add Medication if You Have Been Controlling Entirely Through Diet

If your fasting blood sugar continues to be higher than normal, even after you've lowered your carbohydrate intake, it may be a sign that you are getting past the point where you can control your blood sugar with diet and exercise alone. A swiftly rising fasting blood sugar may be a sign that your beta cells are starting to fail and the best response you can make would be to give them whatever help you can using medications. If you do this as soon as the problem emerges, you may be able to restore beta cell function by giving your beta cells a rest. Wait too long, and those cells will be gone for good.


It is much harder to control your blood sugar when your cells are dead and your fasting blood sugar control is completely gone. So don't wait until you are waking up with blood sugars of 180 mg/dl (10 mmol/L) to consider medication. Any time you can't get near-normal fasting blood sugars with diet alone, it is time to consider medications. I'd suggest talking to your doctor about starting diabetes medications if after making changes that bring your blood sugars after meals into the normal or near normal zone you are still consistently seeing blood sugars over 110 mg/dl (6.1 mmol/L) in the morning.


That is because over the years I've seen that the people with the kind of Type 2 diabetes mainly caused by insulin resistance almost always get truly normal fasting blood sugars (mid-80s 4.7 mmol/L) as soon as they cut way back on carbohydrates. If you can't, there is something more than insulin resistance going on and well-chosen drugs can be a huge help.

If Your Post Meal Numbers Are Normal Don't Fret About High Fasting Readings


Some of us can't get our fasting blood sugars down as low as we'd like. I get a lot of mail from people who find themselves in this situation. Fortunately, the research suggests that if you keep your post meal blood sugars under 140 mg/dl (7.8 mmol/L) most of the time you are very unlikely to develop diabetic complications, even if your fasting blood sugar falls in the range between 110 and 120 mg/dl (6.1 and 6.7 mmol/L).


This is especially true if your fasting blood sugar drops as soon as you've had a meal, as is often the case. In this situation, chalk it up to overly aggressive dawn phenomenon hormones. Remember that these hormones only raise your fasting blood sugar for two or three hours at most, and nothing terrible will happen to you with a couple hours of blood sugars in that range.


The reason that fasting blood sugars over 100 mg/dl (5.6 mmol/L) are associated with poor outcomes in the research is that most people who have those kinds of fasting blood sugars also have post-meal blood sugars surging up to 180 mg/dl (10 mmol/L) or higher after every meal, which we know does cause complications over time. But if your elevated fasting numbers are not associated with hig post meal numbers, and your readings throughout the rest of the day are mostly under 110 mg/dl (6.1 mmol/L) a few hours after eating, you should be fine.

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